Large over the road vehicles such as tractor-trailer trucks frequently are used to transport cargo over great distances. During these long runs the drivers of these vehicles take periodic rest breaks and often sleep in the vehicle. In order to accommodate this, the passenger compartment of a tractor-trailer vehicle is typically divided such that it has a bunk or sleeper area just behind the cab of the truck. This sleeper area can be separated from the cab by a divider such as a curtain.
Generally, the vehicle also includes some sort of heating, ventilation, and air conditioning system that maintains the temperature in the sleeper area at a comfortable level while the driver is sleeping. Presently, there are several different types of heating and air conditioning systems that can be used for this purpose. One way to maintain the appropriate temperature in the sleeper area, simply is to use the heating and air conditioning system of the vehicle. This can be done either by leaving the truck running in idle while the driver sleeps or by "superheating" or "supercooling" the sleep area prior to shutting off the truck engine. However, both of these approaches have significant drawbacks. For example, running the truck in idle while the driver sleeps generates both air and noise pollution, requires a significant amount of fuel, and unnecessarily wears the engine parts. Likewise, superheating or supercooling of the sleeper area is only effective for a short period of time or when the temperature of the outside air is mild.
Another method for heating and cooling the sleeper compartment is to use a heating and air conditioning system which is auxiliary in nature in that it is capable of operating when the engine of the truck is shut off. For example, proposals have been made for heating and air conditioning the sleeper compartment which involve what will be termed "passive" auxiliary systems in that they use thermal storage media to store thermal energy during normal operation of the truck and then deliver that thermal energy in the form of heating or air conditioning when the engine of the truck is shut down. While these systems use some of the same components which are utilized in the present system, the components are used in a different manner, in that the passive nature of the system requires that sufficient energy be stored during normal operation of the truck to provide heating and air conditioning when the engine is shut down. Thus, these types of systems can only heat or cool the passenger compartment for a limited period of time. In particular, in order to heat or cool the sleeper area for a prolonged period of time, the thermal storage media must be charged by the operation of the truck for a prolonged period. More significantly, the thermal storage media must be capable of storing a large amount of thermal energy. Therefore, using this type of system to heat or cool a sleeper area for a prolonged period would likely impose cost, weight, and space requirements that are unacceptable.
In contrast to passive systems, heating and air conditioning systems which are "active" are those systems which are connected to their own independent power source and do not rely on any sort of thermal storage media. Thus, these systems have a relatively unlimited supply of energy to drive the heating air conditioning system for as long as needed. Active heating and air conditioning systems are well known in stationary installations. Typically stationary installations utilize furnaces for heating and compressor driven air conditioners for air conditioning. Some systems use common elements for both heating and air conditioning such as the heat pump. In general, however, these systems are stationary, and have fixed connections, particularly in the case of conventional air conditioners which must have connections to fixed electrical power sources in order to provide the relatively large amounts of power needed to drive the system.
As a result of the need for a sufficient power source, using active heating and air conditioning systems as auxiliary systems for motor vehicles present a different array of problems from passive systems. In particular, in a motor vehicle there is no massive electrical generating capacity which is capable of driving a conventional air conditioner when the engine is shut down nor is there a fixed heat sink such as is required by a heat pump. Fuel fired heaters have been capable of solving this problem for auxiliary heating systems, but insofar as applicant are aware, no active auxiliary refrigeration system has been available for dealing with the air conditioning problem. In order to drive a conventional rotary compressor driven auxiliary air conditioning system which is capable of producing the approximately 2,000 BTU/hr of cooling energy necessary for air conditioning a typical passenger compartment, a fairly large energy source must be incorporated into the motor vehicle.
Sorption cooling systems are also known, and it is known that they use the adsorption/desorption process to drive refrigerant around a refrigerant loop thus eliminating the need for a high powered rotary compressor. Insofar as applicants are aware, sorption cooling has certain niche applications, typically in fixed installations for specialized air conditioning and refrigeration requirements. Sorption air conditioning systems are generally driven by some type of heater. In smaller systems it is generally preferable to use an electric resistance heater. However, as the sorption system gets larger, the electric heater has to draw more power to operate the system. As a result expensive wires, switches, and controls which are capable of handling large currents must be provided. Thus, in larger sorption systems, steam heat from a boiler is generally used to drive the system.